The principal objectives of the proposed investigation are to (A) study the tissue distribution and cellular localization of Beta-ecdysone using a purified antibody to ecdysone and (B) study the biosynthesis and catabolism of tetradecasphing-4-enine in vivo, in vitro (cultured hepatopancreas and nerve cord), and in cell free systems. The cyclic growth and development of crustaceans, as illustrated by the periodic shedding of their exoskeleton, is controlled by Beta-ecdysone. Using a recently developed radioimmune assay in conjunction with fluorescent and electron dense labelling of the purified antibody, we hope to elucidate not only the time of synthesis and release in crustaceans but also to examine tissue and subcellular distribution of this molecule. Because of this molting process and subsequent increase in tissue mass, membrane lipids are synthesized at different rates during the ecdysial cycle. These studies will attempt to elucidate control mechanisms involved in the synthesis of at least one membrane component, i.e., tetradescasphing-4-enine which accounts for 79 percent of the sphingolipid bases in these organisms.